Closure for containers

ABSTRACT

The closure for containers includes a resilient stopper combined with an uninterrupted resilient enclosure member which encloses a piercing area thereon and is positioned between the top surface of the stopper and an overlying resilient flat disc. A rigid plate in turn overlies the flat disc, and the stopper may be retained on the neck of a container by a stopper retainer or ring which overlies the top of the stopper outboard of the enclosure member. An outer sealing ring or tear-off cap secures the closure components together and forces the enclosure member into either the resilient flat disc, the resilient stopper, or both.

United States Patent Cutter et al.

[ Feb. 19, 1974 CLOSURE FOR CONTAINERS [75] Inventors: Robert K. Cutter, Berkeley; Roger A. Saut, San Francisco, both of Calif.

[73] Assignee: Cutter Laboratories, Inc., Berkeley,

Calif.

[22] Filed: Oct. 4, 1971 [21] Appl. No.: 186,061

[52] US. Cl. ..215/247, 215/38 R, 2l5/DIG. 3, 215/256,215/273,2l5/34l,215/358 [51] Int. Cl 865d 51/00 [58] Field of Search 215/37 R, 38 R, DIG. 3

[56] References Cited UNITED STATES PATENTS 3,067,898 12/1962 Reimann 215/37 R 3,088,615 5/1963 Mumford et a1. 215/37 R 2,804,224 8/1957 Barton 215/37 R Heyne et a] 215/38 R Nesset 215/38 R 5 7 ABSTRACT The closure for containers includes a resilient stopper combined with an uninterrupted resilient enclosure member which encloses a piercing area thereon and is positioned between the top surface of the stopper and an overlying resilient flat disc. A rigid plate in turn overlies the flat disc, and the stopper may be retained on the neck of a container by a stopper retainer or ring which overlies the top of the stopper outboard of the enclosure member. An outer sealing ring or tearoff cap secures the closure components together and forces the enclosure member into either the resilient flat disc, the resilient stopper, or both.

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INVENTOR5 Robert K. CuHer BY Roger A. Sour [Sandi W ATTORNEY CLOSURE FOR CONTAINERS BACKGROUND OF THE INVENTION This invention relates to an improvement in a closure for containers of sterile material and in particular to a closure for parenteral solutions containers.

The majority of containers for parenteral solutions now in use employ one of three types of closures. The first constitutes a screw-on closure with a resilient disc contacting the top only of a bottle closed thereby. In use, the closure is unscrewed and removed and an injection set, fitted with a screw-on attachment, is substituted therefor. In the interim between the opening of the bottle and the application of the injection set, the bottle contents are susceptible to contamination.

The second closure type includes a combination of the closure referred to above with a stopper having one or more through passages for air entry and/or for the introduction of injection equipment. Normally parenteral solutions are stored under vacuum, and with removal of the resilient disc from the top of the stopper, air rushes into and through the solution and the bottle contents may accordingly become contaminated.

The final closure type is one in which a resilient pierceable closure is used. Such a closure is usually a solid, one piece stopper with a flange to seal to the top of the container neck, and a thinned piercing area. The stopper is held to the bottle by a crimped outer retaining ring of metal. The top of the stopper and retaining ring are usually found covered with a metal plate and a secondary crimped tear-off metal seal to hold the plate in firm contact with the stopper. In use, a sterile injection set is fitted with a two-hole spike which pierces the stopper and allows the entry of filtered air and the exit of sterile material, This invention relates to the third type of closure.

In the use of parenteral solutions in large volume (usually one liter containers, but may be more or less), total sterility is of paramount importance for the welfare of the patient. To insure this sterility, it is necessary to reach a sufficient temperature for a sufficient period of time in a heat sterilization cycle. Unfortunately, however, if these solutions are allowed to cool normally, many of them are degraded by the prolonged heatv For example, dextrose solutions, which are very commonly used, tend to carmelize and become brown. Because of this, the containers after heat sterilization are subjected to water spray to bring the temperature down rapidly.

Spray-cooling water is not sterile, and if any touches the pierceable area of the top of the stopper, the stopper may become contaminated. Therefore, if the top of the stopper is not later sterilized at the time of use, the normal piercing of the closure with a spike of an injection set will carry the contamination into the intravenous solution.

While this may be of little importance in the usual sterile vial containing 1 cc. to cc. ofa solution which is normally injected in a matter of seconds, it becomes of great importance of the contamination is introduced into a solution which may be injected intravenously over a period of hours, during which time contaminating micro-organisms could multiply significantly.

It was previously thought that by providing an annular projection on the top o-fa resilient stopper, an overlying metal plate held tightly against this projection would be sufficient to allow the top of the stopper to be sterilized during the sterilization procedure and to prevent the spray-cooling water from contaminating the top of the stopper. This has proved fallacious.

In spite of many pounds of head pressure applied to the closure during container sealing, the contact of the non-resilient metal plate against the resilient annular projection has been insufficient to protect the sterility of the piercing area, probably because of the great variation in temperature and pressure developed during the sterilization and spray-cooling procedures. Contamination has occurred with this type of closure and has caused serious reactions.

Recognizing this, the Food and Drug Administration of the United States has requested that all literature and direction sheets for the use of parenteral solution containers with resilient, pierceable closures, instruct the user to swab the top of the stopper with antiseptic fluid before piercing. The FDA. recognizes that this rarely, if ever, sterilizes the top of the stopper, but the hope is that if it is well done' it will materially reduce the number of viable organisms. However, if improperly done, swabbing may fail to reduce the number of organisms and may even introduce further contamination.

Furthermore, in routine use the valuable time of the physician or his assistant is wasted in proper swabbing techniques. In emergencies (and intravenous infusions are an important part of many emergency procedures) the delay can be calamitous.

It is a primary object of the present invention to provide a novel and improved closure for containers which includes a piercing surface which may be sterilized dur' ing the sterilization of the container contents and which is maintained in sterile condition regardless of temperature and pressure changes developed during sterilization and spray-cooling procedures.

Another object of the present invention is to provide a novel and improved closure for containers having a resilient enclosure for a piercing surface which may be positioned to be supported by the end surface of a container mouth to cause deformation of an overlying resilient disc upon the application of pressure thereto.

.A still further object of the present invention is to provide a novel and improved closure for containers which includes a piercing area which is maintained in sterile condition prior to use to eliminate the necessity for swabbing the piercing area with sterilizing material before use.

These and other objects of the present invention will become readily apparent upon a consideration of the following specification and claims taken in conjunction with the accompanying drawings in which:

FIG. 1 is an exploded view of a preferred embodiment of the closure of the present invention;

FIG. 2 is a sectional view in elevation of the closure of FIG. 1;

FIG. 3 is a sectional view of a modification of the stopper and resilient disc employed in the closure of the present invention;

FIG. 4 is a sectional view of a second modification of the stopper and resilient disc employed in the closure of the present invention;

FIG. 5 is a sectional view of a third modification of the stopper and resilient disc employed in the'closure of the presentinvention;

FIG. 6 is a sectional view of an O-ring interposed between the stopper and resilient disc employed in the closure of the present invention; and

FIG. 7 is a cross sectional view of another embodiment of the resilient disk of this invention.

Referring now to the drawings, the closure of the present invention indicated at 10 includes a stopper 12, a stopper retainer 13, a resilient disc 14, a rigid plate and a tear-off cap 16. The stopper 12 is made of resilient material such as rubber and is dimensioned to fit snugly into the neck of container 11. There is an annular extension 17 on the stopper 12 which has a flat surface 18 designed to seat firmly and tightly against the flat end surface 19 of the neck of container 11. This tight fit of stopper 12 at all surfaces in contact with the inside and top surface of the neck of the container 11, when the stopper is clamped to the neck, provides a hermetic seal which assures freedom from contamination of any kind.

Approximately in the center of the stopper 12 is a piercing portion or pierceable means 21 through which a spike or needle may penetrate. Formed integral with the top surface of stopper 12 is an uninterrupted projection or raised ridge portion 22. This projection may be formed in a variety of shapes when viewed crosssectionally, such as triangular or rectangular, or it may be a half-circle as shown in FIG. 2. Viewed from the top of the stopper, this projection 22 need not be circular as shown in FIG. 1 but maybe square, elliptical, triangular or any other shape. However, the circular configuration is preferred. Although only a single projection 22 is shown, the top surface of the stopper may.

have a second projection of the same height lying close to the first. Also, the projection 22 is preferably located to enclose a maximum stopper surface area within the confines thereof, and preferably the projection lies over some portion of the flat surface 19 of the neck of container 11. However, this projection (or any adjacent secondary projection) is not Over-ridden by the stopper retainer 13. Also near the center of the top surface of stopper 12, a raised portion 23 may be located around the piercing portion 21 to serve to mark the location of the piercing portion. This raised portion 23 may also have a variety of cross-sectional shapes.

In this embodiment, the stopper 12 is additionally secured to the neck of the container 11 by a stopper retainer 13 which engages the top and side surfaces of the extension 17 and the side and bottom surfaces of an extending lip 25 on the neck of the container/This stopper retainer assists in maintaining a tight, leak proof fit between the stopper l2 and the container 11. In some cases, the stopper-container combinations may be tight enough not to require a retainer. The stopper retainer is made of relatively rigid material such as metal or rigid plastic, and in this embodiment is thin aluminum. It will be noted that the thickness of the stopper retainer 13 is such that the top surface of the projection 22 extends well above the top surface of the stopper retainer.

Overlying the top surface of stopper [2 and supported by the projection 22 is a relatively thin, smoothsurfaced wafer or disc 14. This disc 14 is made of a resilient material such as rubber or elastomeric polymer, and in this embodiment is rubber. Overlying disc 14 is a rigid plate 15 made of a material such as metal or rigid plastic, 2: preferred material being aluminum. Although disc 14 and plate l5 are usually separate pieces as illustrated in FIG. 1, they may be adhered one to the other to provide a single piece, such as illustrated in FIG. 7 wherein a metal plate 80 is bonded to the resilient disc 82 in a laminated structure.

Encasing the assembly of members 12, 13, 14 and 15 is a relatively rigid tear-off cap 16 which engages the uppermost surface of rigid plate 15 and the side surface of the stopper retainer 13 with a tight clamping force. The tear-off cap 16 may be made of thin metal or plastic and in this embodiment is thin aluminum. This tearoff cap has a tear-off portion or tab 26 which may be employed to break the ring formed by the cap. The surface 32 of tear-off cap 16 is advantageously of such a width that it engages enough of the-underlying surfaces of the rigid plate 15 to impart a good compressive force on disc 14 overlying the projection 22 of stopper 12.

Preferably, the surface 32 extends inwardly to at least a point overlying the projection 22.

When the components of the closure 10 are secured to the container 11, there is generated a hollow space or cavity 27 which is completely enclosed by the resilient disc 14 and the top surface of the stopper within the projection 22. This top surface may include what is defined as the piercing or target area 28, which is the area on the top of the stopper contained by the raised portion 23. It is this area specifically, as well as the adjacent top surfaces, which is important to maintain in a completely sterile condition.

In another embodiment of the closure means, a resilient stopper 40 having a flat top surface 43 is employed in combination with a resilient disc 41 having a projection 42 on one side thereof. When the two members 40 and 41 are compressed by a suitable overlying rigid plate 15 and tear-off cap 16, a hollow space 44 is formed (FIG. 3) similar to the space 27 of FIG. 2. The surfaces making up this space 44 will also be rendered completely sterile as will be subsequently described.

Still further embodiments of the closure stopper and resilient cover disc therefor are illustrated in FIGS. 4 and 5. These embodiments are similar to the stopperdisc combinations of FIGS. 2 and 3, respectively, except that stoppers 50 and 60 have slight depressions 51 and 61 in their top surfaces generally in the area overlying piercing portions 52 and 62, respectively.

In place of projections in either the stopper or resilient disc as described above, a sterile area between the two members may also be provided by a separate resilient or non-resilient ring 71, such as an O-ring, placed between a stopper and a resilient disc 72, both of whose surfaces are flat (FIG. 6).

In the process of attaching closure 10 to a container 11 filled with sterile parenteral solution, a typical operation involves having the filled container under vacuum with the stopper 12 tightly in place. A small amount of fluid, usually a drop, may be placed on the target area 28 and then the remaining parts of the closure, namely, parts 13, 14, 15 and 16 as an assembled unit, are placed over the stopper. Considerable pressure is exerted on the assembled unit and lower edge portions 29 and 30 of the stopper retainer 13 and tear-off cap 16, respectively, are simultaneously crimped or rolled tightly around a projecting head or rim 31 on the neck of the container 11. By this operation, the resilient disc 14 is pressed firmly against the resilient projection 22 of the stopper 12. This pressure is transmitted as a high, concentrated force of many pounds per square inch on the top of .theprojection 22 resulting in some deformation of this projection into disc 14 to provide a very tight, hermetic seal between these two parts. It is important to minimize the upper contact surface of the projection 22, the lower contact surface of the projection 42, or the upper and lower contact surfaces of the O-ring 71 to provide great force on these contact surfaces to maximize the resulting seal. With previous closures wherein a resilient disc is pressed over a flatsurfaced stopper, the force is distributed over a wide area, there is essentially no deformation of the rubber, and a hermetic seal cannot be consistently or assuredly obtained. The fact that one resilient member presses firmly against another resilient member over a very small area of contact with very large forces assures that the area of contact will remain tightly sealed and prevent external contamination of any kind from entering the spaces 27, 44, 51 and 61.

The container 11 sealed by closure is then subjected to a heat sterilization cycle. During this process, the small volume of fluid which may have previously been placed on the target area 28 is also heated to a point where at least a portion of it will vaporize into steam and kill any bacteria present in the space 27 and contiguous surfaces. The fluid may be a mixture of water and glycerine, for example, about a 50-50 mixture of each and in addition, it may contain a small amount of a mold and bacteria growth inhibitor such as the parabens. The glycerine and water may also serve to lubricate the target area" 28 at the time a needle or spike from a solution administration set is forced through portion 21 below the target area 28. The drop of fluid, in this case glycerine and water, need not be placed on the target area" prior to sterilization. The stoppers are routinely washed and rinsed prior to use and contain enough adsorbed water to provide moisture sufficient to effect steam sterilization of the piercing area of the stopper during the sterilization cycle.

The present invention provides for a closure for containers of parenteral solutions wherein the outer surface of the stopper, in particular the area which is to be pierced, may be rendered sterile and maintained in a sterile condition during the period of storage prior to use as well as providing a stopper which will not allow contamination of the solution from environmental air at the time a spike or needle from an administration'set is inserted through the stopper.

At the time of use, tab 26 is pulled off to release the tear-off cap 16. The rigid plate and the resilient disc 14 are easily lifted off to expose the sterile target area" 28 and adjacent surfaces. The sterile spike or needle of an administration set is then pushed through portion 21 of the stopper l2 and the sterile solution from the container 11 is then ready for delivery to the patient.

We claim:

1. A closure for open ended containers of pharmaceutical preparations comprising:

a solid resilient stopper for insertion in sealing engagement with the open end of said container, said stopper having a generally flat upper surface,

a resilient disc having a generally flat surface on both sides, and adapted to overlie said flat upper surface of said stopper,

and an enclosure means interposed between said resilient disc and the upper surface of said stopper and being formed to completely-enclose and define I an area on the upper surface of said stopper, said enclosure means operating when compression is exerted on upper surfaces of said resilient disc to form a seal between said resilient disc and stopper 5 to maintain a sterile area on said upper surface of the stopper following sterilization of said closure and container, said enclosure means comprising a separate ring interposed between said resilient disc and said stopper.

2. A closure for open ended containers of pharmaceutical preparations comprising:

a solid resilient stopper for insertion in sealing engagement with the open end of said container,

said stopper having a generally flat upper surface,

a resilient disc having a generally flat surface on both sides, and adapted to overlie said flat upper surface of said stopper,

and an enclosure means interposed between said resilient disc and the upper surface of said stopper and being formed to completely enclose and define an area on the upper surface of said stopper, said enclosure means operating when compression is exerted on upper surfaces of said resilient disc to form a seal between said resilient disc and stopper to maintain a sterile area on said upper surface of the stopper following sterilization of said closure and container, said enclosure means being nonresilient.

3. A closure for open ended containers of pharmaceutical preparations comprising:

a solid resilient stopper for insertion in sealing engagement with the open end of said container,

said stopper having a generally flat upper surface,

a resilient disc having a generally flat surface on both sides, and adapted to overlie said flat upper surface of said stopper,

an enclosure means interposed between said resilient disc and the upper surface of said stopper and being formed to completely enclose and define an area on the upper surface of said stopper, said enclosure means operating when compression is exerted on upper surfaces of said resilient disc to form a seal between said resilient disc and stopper to maintain a sterile area on said upper surface of the stopper following sterilization of said closure and container,

and a rigid plate overlying said resilient disc, said rigid plate being integral with said resilient disc.

4. A closure for sealing a container opening contained within a neck extension of the container, comprising stopper means for hermetically sealing the container opening, said stopper means including a solid integral resilient body dimensioned to compressibly and frictionally fit within the container neck to form a tight circumferential hermetic seal with the inner surface of the container neck, said solid integral resilient body including a solid generally planar upper surface extending across the entire container opening and pierceable means for permitting a fluid conduit to penetrate through said solid integral resilient body, said pierceable means including one portion of said generally planar upper surface;

a removable resilient disc having a substantially planar surface adjacent said solid generally planar upper surface of said solid resilient body, said resilient disc beingpositioned in non-interlocking relation with said solid generally planar upper surface to permit removal of said resilient disc without removal of said stopper; removable securing means for removably securing said resilient disc in a compressed condition adjacent said solid generally planar upper surface; and

enclosure means interposed between said resilient disc and said generally planar upper surface to concentrate the compression forces applied by said removable securing means along a narrow continuous path completely surrounding said one portion, said path having a total area substantially less than the total area of said generally planar upper surface to provide a tight hermetic seal around said one portion so long as said resilient disc remains secured, whereby said one portion of said generally planar upper surface may be maintained in sterile condition following sterilization of said disc and stop-per means.

5. A closure as defined by claim 4, wherein said enclosure means includes an integral projection on said solid generally planar upper surface of said stopper means.

6. A closure as defined by claim 4, wherein said en closure means includes an integral projection on said substantially planar surface of said removable resilient disc.

7. A closure as defined by claim 4, wherein said enclosure means includes a closed ring element separate from said removable resilient disc and said stopper means.

8. A closure for open ended containers having an end surface surrounding the open end and extending substantially perpendicular to the longitudinal axis of the container, comprising a solid integral resilient stopper for insertion in sealing engagement with the open end of said container, said stopper including an upper portion having a generally planar upper surface, said upper portion extending laterally over the end surface of the container to contact the end surface when said stopper is inserted in said container, said stopper further in cluding pierceable means for permitting a fluid conduit to penetrate through said solid integral resilient body, said pierceable means including one portion of said generally planar upper surface; first retaining means for compressively securing said upper portion against the end surface ofthe container to maintain a hermetic seal between said stopper and the container; a removable resilient disc having a substantially planar surface adjacent said generally planar upper surface; second retaining means for normally securing said resilient disc in a compressed condition adjacent said planar upper surface and for permitting said resilient disc to be removed without removal of said stopper; and

enclosure means interposed between said resilient disc and said generally planar upper surface to concentrate the compression forces applied by said removable securing means along a narrow continuous path completely surrounding said one portion, said path having a total area substantially less than the total area of said generally planar upper surface to provide a tight hermetic seal around said one portion so long as said resilient disc remains secured, whereby said one portion of said generally planar upper surface may be maintained in sterile condition following sterilization of said disc and stopper.

9. A closure as defined in claim 8, wherein said enclosure means is formed by a first integral projection on said substantially planar upper surface.

10. A closure as defined in claim 9, wherein said solid generally planar upper surface includes a second integral projection immediately surrounding said one portion, said second integral projection being positioned within said first integral projection.

11. A closure as defined in claim 8, wherein said first retaining means includes a first retaining ring engaging the container neck and the upper surface of said resilient stopper outboard of said enclosure means.

12. A closure as defined in claim 8, wherein the closure is adapted for connection with a container having an external locking rim adjacent the open end, and further wherein said second retaining means includes a rigid plate overlying said resilient disc and a tear-off cap overlying said rigid plate, resilient disc and stopper to provide removable compression to said resilient disc, said tear-off cap having a lower edge adapted to be crimped around said locking rim.

13. A closure as defined in claim 12, wherein said enclosure means is disposed over said end surface surrounding the open end of the container and said tearoff cap further includes a surface portion extending inwardly over said enclosure means, whereby said enclosure means may be securely held between the end surface of the container and said lip portion when said tear off cap is crimped to said locking rim. 

1. A closure for open ended containers of pharmaceutical preparations comprising: a solid resilient stopper for insertion in sealing engagement with the open end of said container, said stopper having a generally flat upper surface, a resilient disc having a generally flat surface on both sides, and adapted to overlie said flat upper surface of said stopper, and an enclosure means interposed between said resilient disc and the upper surface of said stopper and being formed to completely enclose and define an area on the upper surface of said stopper, said enclosure means operating when compression is exerted on upper surfaces of said resilient disc to form a seal between said resilient disc and stopper to maintain a sterile area on said upper surface of the stopper following sterilization of said closure and container, said enclosure means comprising a separate ring interposed between said resilient disc and said stopper.
 2. A closure for open ended containers of pharmaceutical preparations comprising: a solid resilient stopper for insertion in sealing engagement with the open end of said container, said stopper having a generally flat upper surface, a resilient disc having a generally flat surface on both sides, and adapted to overlie said flat upper surface of said stopper, and an enclosure means interposed between said resilient disc and the upper surface of said stopper and being formed to completely enclose and define an area on the upper surface of said stopper, said enclosure means operating when compression is exerted on upper surfaces of said resilient disc to form a seal between said resilient disc and stopper to maintain a sterile area on said upper surface of the stopper following sterilization of said closure and container, said enclosure means being nonresilient.
 3. A closure for open endEd containers of pharmaceutical preparations comprising: a solid resilient stopper for insertion in sealing engagement with the open end of said container, said stopper having a generally flat upper surface, a resilient disc having a generally flat surface on both sides, and adapted to overlie said flat upper surface of said stopper, an enclosure means interposed between said resilient disc and the upper surface of said stopper and being formed to completely enclose and define an area on the upper surface of said stopper, said enclosure means operating when compression is exerted on upper surfaces of said resilient disc to form a seal between said resilient disc and stopper to maintain a sterile area on said upper surface of the stopper following sterilization of said closure and container, and a rigid plate overlying said resilient disc, said rigid plate being integral with said resilient disc.
 4. A closure for sealing a container opening contained within a neck extension of the container, comprising stopper means for hermetically sealing the container opening, said stopper means including a solid integral resilient body dimensioned to compressibly and frictionally fit within the container neck to form a tight circumferential hermetic seal with the inner surface of the container neck, said solid integral resilient body including a solid generally planar upper surface extending across the entire container opening and pierceable means for permitting a fluid conduit to penetrate through said solid integral resilient body, said pierceable means including one portion of said generally planar upper surface; a removable resilient disc having a substantially planar surface adjacent said solid generally planar upper surface of said solid resilient body, said resilient disc being positioned in non-interlocking relation with said solid generally planar upper surface to permit removal of said resilient disc without removal of said stopper; removable securing means for removably securing said resilient disc in a compressed condition adjacent said solid generally planar upper surface; and enclosure means interposed between said resilient disc and said generally planar upper surface to concentrate the compression forces applied by said removable securing means along a narrow continuous path completely surrounding said one portion, said path having a total area substantially less than the total area of said generally planar upper surface to provide a tight hermetic seal around said one portion so long as said resilient disc remains secured, whereby said one portion of said generally planar upper surface may be maintained in sterile condition following sterilization of said disc and stopper means.
 5. A closure as defined by claim 4, wherein said enclosure means includes an integral projection on said solid generally planar upper surface of said stopper means.
 6. A closure as defined by claim 4, wherein said enclosure means includes an integral projection on said substantially planar surface of said removable resilient disc.
 7. A closure as defined by claim 4, wherein said enclosure means includes a closed ring element separate from said removable resilient disc and said stopper means.
 8. A closure for open ended containers having an end surface surrounding the open end and extending substantially perpendicular to the longitudinal axis of the container, comprising a solid integral resilient stopper for insertion in sealing engagement with the open end of said container, said stopper including an upper portion having a generally planar upper surface, said upper portion extending laterally over the end surface of the container to contact the end surface when said stopper is inserted in said container, said stopper further including pierceable means for permitting a fluid conduit to penetrate through said solid integral resilient body, said pierceable means including one portion of said generally planar upper surface; first retaining mEans for compressively securing said upper portion against the end surface of the container to maintain a hermetic seal between said stopper and the container; a removable resilient disc having a substantially planar surface adjacent said generally planar upper surface; second retaining means for normally securing said resilient disc in a compressed condition adjacent said planar upper surface and for permitting said resilient disc to be removed without removal of said stopper; and enclosure means interposed between said resilient disc and said generally planar upper surface to concentrate the compression forces applied by said removable securing means along a narrow continuous path completely surrounding said one portion, said path having a total area substantially less than the total area of said generally planar upper surface to provide a tight hermetic seal around said one portion so long as said resilient disc remains secured, whereby said one portion of said generally planar upper surface may be maintained in sterile condition following sterilization of said disc and stopper.
 9. A closure as defined in claim 8, wherein said enclosure means is formed by a first integral projection on said substantially planar upper surface.
 10. A closure as defined in claim 9, wherein said solid generally planar upper surface includes a second integral projection immediately surrounding said one portion, said second integral projection being positioned within said first integral projection.
 11. A closure as defined in claim 8, wherein said first retaining means includes a first retaining ring engaging the container neck and the upper surface of said resilient stopper outboard of said enclosure means.
 12. A closure as defined in claim 8, wherein the closure is adapted for connection with a container having an external locking rim adjacent the open end, and further wherein said second retaining means includes a rigid plate overlying said resilient disc and a tear-off cap overlying said rigid plate, resilient disc and stopper to provide removable compression to said resilient disc, said tear-off cap having a lower edge adapted to be crimped around said locking rim.
 13. A closure as defined in claim 12, wherein said enclosure means is disposed over said end surface surrounding the open end of the container and said tear-off cap further includes a surface portion extending inwardly over said enclosure means, whereby said enclosure means may be securely held between the end surface of the container and said lip portion when said tear off cap is crimped to said locking rim. 